This invention relates generally to apparatus for printing on the exterior surfaces of containers, and more particularly, is directed to an assembly for rotating the mandrels on which the containers are held.
In general, a variety of machines for applying decorative finishes to plastic frusto-conical cups are known. Such machines include an intermittently rotatable mandrel wheel having a plurality of spaced, radially directed mandrels located on the periphery of the mandrel wheel for holding the cups thereon. After each cup is received on a corresponding mandrel at the loading station, the mandrels are intermittently rotated with the mandrel wheel to a pre-treatment station, a printing station, a cure station and finally to an unloading station at which the cup thereat is removed from the respective mandrel. At the pre-treatment station, the plastic cup is subjected to a glass flame or electrical discharge which provides better adherence of the ink to the cup at the subsequent printing station. At the printing station, a printing blanket is brought into contact with each of the cups, to place a decoration on the outer frusto-conical surface thereof, and at the subsequent cure station, the ink is cured by ultraviolet light.
In order to provide a uniform pre-treatment and cure to each cup, the mandrels are rotated or spun at the pre-treatment and cure stations. Conventionally, this has been accomplished by a separate roller mechanism which contacted the mandrel and rotated the same at the pre-treatment and cure stations. Accordingly, a separate motor and roller wheel have conventionally been provided at each station for such purpose. This has proven to be extremely costly and ineffective.
U.S. Pat. No. 4,543,883 discloses an apparatus for printing on frusto-conical cups in which the mandrels intermittently move through 16 different positions for each revolution of the mandrel wheel or turret. During such movement, all of the mandrels are continuously rotated about their respective rotational axis by means of a continuously rotating ring gear which rotates the mandrels through respective pinions. Because of this arrangement, different mandrels cannot be selectively rotated, while not rotating the remaining mandrels.
U.S. Pat. No. 3,934,500 discloses an apparatus for printing on cylindrical or frusto-conical containers with an ultraviolet light ink, in which a turret or mandrel wheel includes a plurality of mandrels spaced therearound. The turret is rotated in synchronism to register each mandrel in turn at a loading station, printing station, drying station, and an unloading station. Each of the mandrels is secured on the outer end of a drive shaft rotatably mounted to the turret, the axis of the shaft being radially disposed. A bevel gear is secured on the inner end of the shaft. Therefore, with this apparatus, all of the mandrels rotate continuously in synchronism with the intermittent indexing movements of the turret, in a manner similar to that of U.S. Pat. No. 4,543,883. See also U.S. Pat. No. 3,645,201, which describes another arrangement in which a gear is permanently in mesh with bevel gears for rotating all of the mandrels.
In addition, with these latter arrangements, the mandrels are rotated by the same drive that drives the machine, that is, the mandrel wheel. It is sometimes desirable to adjust the speed of rotation of the mandrels without changing the rotational speed of the mandrel wheel. This adjustment, however, cannot be made with these machines. U.S. Pat. Nos. 2,425,928; 3,962,970; and 3,977,318 disclose other apparatus for printing on frusto-chonical cups.